(1) Field of the Invention
The present invention relates to an improvement of a process for measuring the contour configurations of articles which configurations are each defined by numerous cylindrical surface portions, such as a honeycomb structural bodies which have an ununiform cylindrical outer surface and are used in purifiers for waste gases from automobiles.
(2) Related Art Statement
In general, honeycomb structural bodies to be used as catalyst carriers for the purification of waste gases from automobiles are conventionally of cylindrical shapes or of elliptically cylindrical shapes. However, honeycomb structural bodies having ununiform cylindrical outer surfaces constituted by numerous different cylindrical surface portions as shown in FIG. 1 have recently come to be used. Since such honeycomb structural bodies need to accurately be set inside their casings, it is necessary to precisely measure the contour configurations thereof.
In order to measure the contour configurations of these honeycomb structural bodies, limit gauges having a size equal to an ideal contour configuration plus an allowable dimensional tolerance are generally used, and whether or not the contour configuration of the honeycomb structural bodies is good or to be rejected is judged based on whether they pass the limit gauge or not. However, since such a contact type measuring process may damage surfaces of thin wall products, such as honeycomb structural bodies, this process is not favorable.
Under the circumstances, as shown in U.S. Pat. No. 4,298,285, DE No. 2,926,140C and GB No. 2,030,286B, NGK Insulators, Ltd. has already developed an apparatus for measuring the contour configuration of honeycomb structural bodies. That is, as shown in FIGS. 7 and 8, the apparatus for measuring the contour configuration of articles comprises a turntable 6 on which an article 5 to be measured is to be placed and which is rotated around a rotary shaft 8 by a motor 9 through a gear mechanism 10, a detector 11 for detecting the rotational angle of the turntable to produce a rotational angle signal, an edge detector including a parallel light-projecting member 12 for projecting parallel light beams onto the article, a parallel light-receiving member 13 for receiving a part of the parallel light which is not shielded or cut by the article to produce an edge position signal, a memory 16 for storing a standard edge position signal which corresponds to a standard article having a given contour configuration, and an operation circuit 15 for receiving the rotational angle signal. The parallel light-projecting and -receiving members are arranged on opposite sides of the turntable. The edge position signal and the standard edge position signal produce a signal which represents the deviation in the contour configuration of the article to be measured from the standard article. Reference numerals 11 and 17 denote a rotary endode and an operation circuit 15, respectively. The article is guided on the turntable by a guide plate 7. However, since this conventional apparatus is directed to cylindrical or elliptically cylindrical articles, the apparatus requires that the central point of the cylindrical or elliptically cylindrical surface constituting the outer periphery is present on an X-axis or a Y-axis. Therefore, this apparatus cannot unfavorably perform accurate measurement of articles having some of center points O.sub.1 to O.sub.7 deviated from the X-axis and the Y-axis as shown in FIG. 3. That is, according to the above prior art technique, a rotational angle of the turntable at which a curve of the parallel beam-interrupted location exhibits a peak is obtained when the turntable is rotated, and deviation in a set angle of the article on the turntable is corrected. As to the article having a shape shown in FIG. 1, the curve gently changes, so that the location of the peak cannot accurately be read.